Math Problem Statement

Write each of the given numbers in the polar form re^(iθ), -π < θ ≤ π

Solution

The image shows a complex number in rectangular form that needs to be converted to polar form. I see three parts:

(a) 7i3\frac{7 - i}{3}

(b) 4π(4+i3)-4\pi (4 + i\sqrt{3})

(c) (1+i)6(1 + i)^6

The goal is to find the polar form for each expression.

Let me go through them step by step.


(a) 7i3\frac{7 - i}{3}

For this, we convert the complex number to polar form by finding its modulus (r) and argument (θ).

Step 1: Compute the modulus rr

The modulus rr is found by using the formula: r=a2+b2r = \sqrt{a^2 + b^2} For 7i7 - i, a=7a = 7 and b=1b = -1, so: r=72+(1)2=49+1=50r = \sqrt{7^2 + (-1)^2} = \sqrt{49 + 1} = \sqrt{50} Now, divide by 3 as the number is scaled by 1/3: r=503=523r = \frac{\sqrt{50}}{3} = \frac{5\sqrt{2}}{3}

Step 2: Compute the argument θ\theta

The argument θ\theta is the angle the complex number makes with the positive real axis. Use the formula: θ=tan1(ba)\theta = \tan^{-1} \left(\frac{b}{a}\right) Here, a=7a = 7 and b=1b = -1, so: θ=tan1(17)0.1419\theta = \tan^{-1} \left(\frac{-1}{7}\right) \approx -0.1419

So, the polar form of 7i3\frac{7 - i}{3} is: r=523,θ0.1419r = \frac{5\sqrt{2}}{3}, \quad \theta \approx -0.1419


(b) 4π(4+i3)-4\pi (4 + i\sqrt{3})

First, simplify the expression inside the parentheses: 4π(4+i3)=16π4πi3-4\pi (4 + i\sqrt{3}) = -16\pi - 4\pi i \sqrt{3}

Now, find the modulus rr and argument θ\theta for the complex number 16π4πi3-16\pi - 4\pi i\sqrt{3}.

Step 1: Compute the modulus rr

r=(16π)2+(4π3)2=(256π2)+(48π2)=304π2=π304r = \sqrt{(-16\pi)^2 + (-4\pi \sqrt{3})^2} = \sqrt{(256\pi^2) + (48\pi^2)} = \sqrt{304\pi^2} = \pi \sqrt{304} Approximating 304\sqrt{304} gives: r54.776r \approx 54.776

Step 2: Compute the argument θ\theta

θ=tan1(4π316π)=tan1(34)0.409\theta = \tan^{-1} \left(\frac{-4\pi \sqrt{3}}{-16\pi}\right) = \tan^{-1} \left(\frac{\sqrt{3}}{4}\right) \approx 0.409

So, the polar form of 4π(4+i3)-4\pi (4 + i\sqrt{3}) is: r54.776,θ0.409r \approx 54.776, \quad \theta \approx 0.409


(c) (1+i)6(1 + i)^6

We first convert 1+i1 + i to polar form and then raise it to the power of 6.

Step 1: Convert 1+i1 + i to polar form

For 1+i1 + i, the modulus is: r=12+12=2r = \sqrt{1^2 + 1^2} = \sqrt{2} The argument is: θ=tan1(1)=π4\theta = \tan^{-1}(1) = \frac{\pi}{4}

So, the polar form of 1+i1 + i is: r=2,θ=π4r = \sqrt{2}, \quad \theta = \frac{\pi}{4}

Step 2: Raise to the power of 6

To raise a complex number in polar form to a power, we use: rn(cos(nθ)+isin(nθ))r^n \left( \cos(n\theta) + i\sin(n\theta) \right) Thus, (1+i)6(1 + i)^6 is: r6=(2)6=8,θ6=6π4=3π2r^6 = (\sqrt{2})^6 = 8, \quad \theta \cdot 6 = \frac{6\pi}{4} = \frac{3\pi}{2}

So, the polar form of (1+i)6(1 + i)^6 is: r=8,θ=3π2r = 8, \quad \theta = \frac{3\pi}{2}


Would you like further clarification or details on any of these steps?

Here are some related questions for deeper understanding:

  1. How do you compute the argument of a complex number in a different quadrant?
  2. How does Euler's formula relate to polar form of complex numbers?
  3. What is the significance of the argument in trigonometric identities?
  4. How do you handle negative complex numbers when finding their polar form?
  5. What happens when you raise a complex number to a power in polar form?

Tip: Always ensure to check which quadrant your complex number is in before computing the argument!

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Polar Form of Complex Numbers
Modulus and Argument of Complex Numbers

Formulas

r = √(a² + b²)
θ = tan⁻¹(b/a)
De Moivre's Theorem: (r(cos θ + i sin θ))^n = r^n (cos(nθ) + i sin(nθ))

Theorems

De Moivre's Theorem
Polar Representation of Complex Numbers

Suitable Grade Level

Grades 11-12